Motor-driven pumps with rotary pump and turbine drive are already known. These motor-driven pumps are distinguished not only by the types of pumps used and by the model of the turbine, but also by the mutual arrangement of the turbine and of the pump, and ipso facto, by the mechanical transmission of the movement between these two constituent parts of the motor-driven pump.
Motor-driven pumps are known, in particular, in which the turbine and the pump are disposed in line, that is to say that the axis of the pump and the axis of the turbine are placed in the extension of one another. In such motor-driven pumps, at least one of the two (inlet and outlet) pipes of the pump is disposed perpendicularly or obliquely relative to the axis of the pump, whereas the second pipe is disposed either perpendicularly or obliquely relative to the axis of the pump, or in line with the axis of the pump (on the side of the pump located opposite the turbine).
Application DE-A-3,008,334 describes a tangential turbine driving a pump the rotary body of which is formed by the hollow shaft of the turbine; the machine described in Application DE-A-3,008,334 operates with steam; the machine described is bulky and adapted solely to a static use.
Document CH-465,413 describes a single-axis pump intended for a fixed installation in an atomic power station. The pump is actuated by a peripheral turbine. The pump rotor is of the type with central hub, supported by bearings which encroach on the available cross-section, without possible mixing between the motive fluid and the pumped fluid.
U.S. Pat. No. 2,113,213 describes cylindrical pumps formed by a small rotary pump and by a concentric turbine. These pumps are intended to operate in wells in order to extract water or oil therefrom. These pumps, mounted in series, are placed in a chamber and sunk under the layer to be pumped. Each pump is provided at its base with vents. When a pressurised fluid is injected into the chamber, it rises through the vents, setting the turbine in rotation and thus actuating the pump. The motive fluid subsequently mixes completely with the pumped liquid in order to rise to the surface.
For some applications, the motor-driven pumps known at the present time all have serious disadvantages; this is especially true of submerged motor-driven pumps used for dredging operations.
In suction dredgers, the boom is equipped with a suction pipe intended for conveying the dredged materials (mud, and/or sand) into the wells of the dredger or into delivery pipes.
Suction can be carried out by a motor-driven pump mounted on board the dredger. However, such a system is suitable only for relatively small dredging depths.
For dredging at greater depth, it is usually necessary to employ a submerged motor-driven pump mounted as low as possible on the suction pipe.
Such a submerged motor-driven pump thus works under pressure, and therefore its suction performance is improved. However, the use for such applications of the motor-driven pumps known at present presents very serious technical problems due in particular to the high weight and large bulk of these motor-driven pumps and of the elbowed pipes connected thereto. Thus, a submerged motor-driven dredging pump which can be connected to pipes of a diameter of 650 mm currently represents a weight of the order of 25 tons, a length of 6 m and a lateral dimension of 3 m (including the elbowed pipes and the frame necessary in order to absorb the stresses generated during manoeuvring and operation). The manoeuvring of a dredging head equipped with such a motor-driven pump of known type requires the use of heavy and costly handling machinery, and a great deal of skill.
Another problem arises because of the (mechanically speaking) difficult environment in which these motor-driven pumps have to be used, namely generally aggressive water, such as seawater, laden with salt and with particles of varied granulometry.
In order to protect the delicate parts of these motor-driven pumps, sealing devices of extremely high performance are generally employed, particularly in order to protect the rolling bearings and the elements of the turbine, thereby proportionately increasing the weight and bulk and also presenting problems of cost, of ease of maintenance and of heat dissipation.
The same inventor's Patent EP-0,033,640 describes a motor-driven pump with turbine actuated by a pressurised fluid more particularly adapted to dredging operations in which the pump and the turbine are disposed in a concentric manner, the motive fluid and the pumped liquid passing through the motor-driven pump in an axial direction. A motor-driven pump, in accordance with EP-0,330,640, despite its qualities, does not yet solve all the problems. In comparison with its power, it is still fairly voluminous and extended in length, which implies a high cost (in weight of metal), and the use of relatively costly handling machinery; it necessitates a high volume of motive fluid and therefore feed pipes of large diameter, entailing a substantial extra weight. Its size still renders it sensitive to the stresses generated during manoeuvring and in service. Furthermore, disassembly of the various members still requires a non-negligible time whereas, precisely, in the working conditions to which it is subjected, these disassemblies are relatively frequent. Lastly, the range of regulation of such a motor-driven pump is, in practice, fairly narrow, which does not make it possible to adapt in an optimal manner to all circumstances arising in service (increasing the load, fitting pumping members of a different kind).
The motor-driven pump according to the invention, which will be described below, can be used in particular as a submerged motor-driven pump and is in particular highly advantageous as a submerged motor-driven pump for dredging and for working marine sediments at great depth. However, the application of the motor-driven pump according to the invention is by no means limited to these particular examples, and it can also be used advantageously as a non-submerged motor-driven pump for pumping various liquids or liquids laden with solids (for example, suspensions of ores and/or coal in water).
An endeavour has been made to construct a motor-driven pump having, for an equal suction power, greater compactness in length and a weight reduced in comparison with what was known in the state of the art.
Another object of the invention is to obtain a very strongly built motor-driven pump, self supporting by virtue of its structure per se, and resisting axial stresses and torsion and flexion alike.
Another object of the invention is to produce a motor-driven pump which permits easy control of the turbine speed and, thereby, of the flow rate and of the pressure of the pumped liquid.
The invention also has as its subject a motor-driven pump of lesser production cost, for equal power, than what is known in the state of the art.
Another object of the invention is to produce such a motor-driven pump which can be used advantageously for the pumping of liquids heavily laden with solids and consequently being suitable as motor-driven pumps for dredging or for working sea bed sediments.
In addition, the invention has the object of providing such a motor-driven pump in which the energy losses are reduced in a substantial manner.
Another object of the invention is to construct a motor-driven pump the bearings of which are protected in an effective manner with regard to their conditions of use.
Lastly, another subject of the invention is a motor-driven pump of low maintenance cost the members of which can easily be replaced.